EP3771053A1 - Arcing fault monitoring device, particularly for low-voltage switchgear - Google Patents

Abstract

The invention relates to an arc fault monitoring device, in particular for low-voltage switchgear with feeder panels and output panels (1). The invention is characterized in that a detection and calculation module (6) is arranged in the output panels (1) or in each of the branches (2) therein , which measures a current flow, evaluates it per unit of time and reliably differentiates an arc fault that has occurred in front of the respective protective device from a normal short circuit.

Description

The invention relates to an arcing fault monitoring device, in particular for low-voltage switchgear with feeder panels and output panels.

Low-voltage switchgears usually consist of feeder panels, couplings and output panels. A feed switch, usually an ACB, is usually installed in the feeder bays, which protects the system from short circuits, overloads and internal faults. The outgoing fields often contain several branches for controlling the connected consumers. A main switch is located on each of the branch modules as a protective device, which in turn protects the branch from short circuit, overload and internal faults downstream of a protective device.

In the event of faults in front of these protective devices, in particular primary faults, or if these fail, the feed switch of the switchgear must switch off the fault. The switch-off times of these ACB circuit breakers used as feed switches from the occurrence of a fault are in practice approx. 50 ms and more. In the event of an internal fault on a feeder, the damage to the switchgear caused by the arcing fault is already considerable after this time.

In recent years, arc fault monitoring devices have become established for low-voltage switchgear, which react to flashes of light caused by arcing or flashes of light and an increase in current and lead to shutdown after a few milliseconds. However, monitoring the functional areas of the branches using flashes of light is problematic, since even with normal short-circuit shutdowns by the switches, mostly MCCBs, or fuses, flashes of light are generated, which can then lead to false messages, which lead to the inadvertent shutdown of the entire switchgear. If the entire low-voltage switchgear were switched off, all consumers connected to it would fail. However, this is only acceptable in the case of an arc fault on the primary side, i.e. in front of the protective device in the branches, in the switchgear.

• Die Funktionsräume mit MCCB's können wegen des Risikos der Fehlauslösung bei einer Kurzschlussabschaltung nicht über die Erfassung von Lichtblitzen auf Störlichtbögen überwacht werden. Die Störlichtbögen können erst durch Abschaltung des Einspeiseschalters (ACB) in der Niederspannungsschaltanlage nach >50ms gelöscht werden.
• Ein Störlichtbogen in diesen Funktionsräumen lässt sich auf Grund der freigesetzten Energie nur für einen gewissen Zeitraum auf das Abzweigfach begrenzen.
• Bei Einschüben, insbesondere unter Spannung auswechselbaren Abzweigen, führt ein nicht schnell erfolgter Abschaltvorgang des Störlichtbogens auf Grund der zu hohen Energie zu einem Abbrennen der eingangsseitigen Steckkontakte. Dabei wird auch die Feldsteckschiene beschädigt und muss bei einer Reparatur aufwendig getauscht werden.

Bei aktuellen Niederspannungsschaltanlagen ist zwar ein gewisser Personenschutz bei einem Störlichtbogen im Abzweigfach gegeben, jedoch können bei länger brennenden Störlichtbögen Verbrennungen nicht ganz ausgeschlossen werden.So far, the following problems have arisen:

• The function rooms with MCCBs cannot be monitored by detecting flashes of light for arcing due to the risk of false tripping in the event of a short-circuit shutdown. The arc faults can only be extinguished by switching off the feed switch (ACB) in the low-voltage switchgear after> 50ms.
• An arc fault in these functional rooms can only be limited to the junction compartment for a certain period of time due to the energy released.
• In the case of plug-in units, in particular branches that can be exchanged under voltage, if the arc fault does not switch off quickly, the plug-in contacts on the input side burn off due to the excessive energy. The field connector rail is also damaged in the process and must be replaced at great expense in the event of a repair.

In current low-voltage switchgear systems, there is a certain level of personal protection in the event of an arc fault in the junction compartment, but burns cannot be completely ruled out if the arc fault occurs for longer periods.

The well-known arc fault monitoring devices, which can switch off an internal fault very quickly, react to flashes of light and optionally also to an increase in current. In the short-circuit disconnection of an MCCB, the system cannot distinguish between a normal short circuit and a primary-side arc fault in the short time required. Arc fault protection of the outgoing panels by detecting light flashes is currently only possible safely for rooms without a circuit breaker. The field rail could be protected from internal faults by installing a protective device at the feed point, but this solution requires a lot of space and can cause problems with regard to the selectivity of the switches in the feeders.

For this reason, only the main busbars, field distribution bars and cable connections are monitored by arc fault detection devices, but not the compartments with the feeders. So far, no practicable solution is known which safely monitors the compartments with the feeders for arcing faults on the primary side and excludes false triggering.

At present there is also no known monitoring system which reliably detects faults such as arcing faults on withdrawable units and switches them off so quickly that the input-side isolating contacts in the withdrawable unit or the plug-in rail in the field are reliably protected from overload.

Accordingly, the object of the present invention is to create an arc fault monitoring device, in particular for low-voltage switchgear, which reliably detects a faulty current flow in the outgoing panels and triggers a disconnection process.

This object is achieved according to the invention by an arc fault monitoring device, in particular for low-voltage switchgear assemblies according to claim 1. Advantageous training and development, which can be done individually or in combination can be used are the subject of the dependent claims.

According to the invention, this object is achieved by an arc fault monitoring device, in particular for low-voltage switchgear, with feeder panels and output panels. The invention is characterized in that a detection and calculation module is arranged in the outgoing bays or in each of the branches located therein, which measures a current flow, evaluates it per unit of time and reliably differentiates an arcing fault occurring in front of the respective protective devices from a normal short circuit.

The essence of the invention is to determine the flowing electrical currents at very short intervals and to evaluate them with the help of a fast acquisition and calculation module. It is also possible to determine the I ² x t values per unit of time in the microsecond range. Fuses or MCCBs (molded case circuit breakers) are preferably used as protective devices for the branches. Both types of device limit the maximum flowing short-circuit current and switch off a short-circuit after a few milliseconds. The maximum I ² x t values flowing for each switch type, i.e. the squared current per unit of time, are known and can be used as a reference variable.

If the flowing currents are greater than the current limit of the corresponding protective devices, there can only be a fault in or in front of them. After evaluating the shutdown curves, such an error can be detected after approx. 1.5 ms. In the case of small short-circuit currents, errors can be detected via the I ² x t values per unit of time, for example 3 ms, if these clearly exceed the normal values of the protective devices. Even with very small short-circuit currents, errors can be reliably detected by looking at the I ² x t values over a longer time interval if the values are significantly higher than the protective devices allow. If the acquisition and calculation module determines that there must be an internal primary fault on the basis of the evaluated data, this can short-circuit the system in a few milliseconds via an AQD device (Arc Quenching Device) installed in the system and thus extinguish the arc fault. The power is switched off downstream via the feed switch in the system.

Alternatively, a fast isolator could interrupt the flow of current. This also avoids major damage to the switchgear. Incorrect triggering due to light flashes generated elsewhere in the system can be excluded.

With withdrawable branches, the isolating contacts of the withdrawable units are designed to carry the maximum forward currents or the I ² x t values of the respective protective device. Previously, in the event of a primary fault on a branch, the isolating contacts could no longer carry the high energies and were destroyed, which also damaged the field rail. In order to repair the damage, the entire field rail had to be laboriously removed and replaced. With the new monitoring device according to the invention, damage to the isolating contacts and the field rail can be avoided through the timely detection of an internal primary fault and the rapid arc fault extinction via an AQD.

The current can be measured, for example, by a Rogowski coil. These Rogowski coils require little space and can therefore be easily integrated into existing switchgear. This current measurement can be integrated into the switchgear at the electrical connection between the main busbar and the field rail and thus centrally monitor an entire outgoing feeder panel for primary faults, or at the connection between the field rail and the branch to monitor individual branches. This latter possibility is mainly for branches Interesting in withdrawable technology, as it can be used to ensure that the permissible values per unit of time are adapted to the respective contact system and therefore not exceeded. This means that contact systems for feeders with lower currents can also be safely protected in the event of a fault in front of the protective device on the feeder.

The arc fault monitoring device according to the invention is characterized in that arcing faults or faults in front of the branch protection device are detected by monitoring and evaluating the currents and I ² x t values in outgoing panels or branches of low-voltage switchgear. If significantly higher I ² x t values are recorded than the protective devices in the outgoing bays or on branches allow, there must be a primary-side fault or a failure of the protective device. If such an error is detected, an AQD is activated and the infeed switch or a high-speed disconnector is triggered, whereby the error is switched off within a few milliseconds. The resulting damage is minimized through the rapid detection and deactivation of a primary fault. The field rail and the plug-in contacts on the input side are thus protected from damage.

This solution makes it possible to reliably protect a main circuit from the tap from the main busbar or field bar with all devices from internal errors or the consequences of errors in the form of backup protection. This proposed solution is particularly interesting for motor control centers with feeders that can be removed under voltage as plug-in units. These plug-in units have an input contact system that is designed for the permeability characteristics of the protective devices (MCCB, fuse) installed on these branches. If the permissible let-through energy is significantly higher than that of the devices on the feeder, the contact system can be safely protected from an excessive, critical energy flow, which only occurs in the event of a fault can occur. With the solution described, the switching time of the AQD must be taken into account when designing the contact system for the set I ² x t limits.

In practice, if a primary arc fault with too high a flow energy is not detected and switched off in good time, the contact system at the current transition to the mostly vertically arranged field distribution rail will melt. This not only damages the contact, but also the field distribution bus. This can only be exchanged when the switchgear is de-energized. This solution therefore also enables reliable protection of the field distribution bus, which can significantly increase the availability of the low-voltage switchgear.

An advantageous embodiment for the concept of the arc fault monitoring device according to the invention can consist in the acquisition and calculation module determining and evaluating the I ² * t values in the microsecond range.

A continuation of the concept according to the invention for the arc fault monitoring device can consist in that fuses and / or MCCBs (Molded Case Circuit Breakers) and / or other current-carrying elements with a protective function and / or current-carrying elements with a protective function at least one further function as a protective device in the branches , so a combined device, are arranged.

An extension of a special embodiment of the concept according to the invention for the arc fault monitoring device can provide that a current flow above a current limit specified by the protective devices for a regular current flow is stored as a faulty current flow in the detection and calculation module.

An advantageous embodiment for the inventive concept of an arc fault monitoring device can consist in that a short circuit is to be generated by means of an AQD device (Arc Quenching Device), which leads to a voltage drop in the system and to the extinguishing of the arc, ie in order to determine To extinguish the arc fault immediately

A continuation of the concept according to the invention for the arc fault monitoring device can consist in switching off the current flow downstream of the short circuit through the AQD via a feed switch.

An extension of a special embodiment of the concept according to the invention for the arc fault monitoring device can provide that a shutdown of the current flow downstream of the short circuit via a fast disconnector or a disconnector or a current-carrying element with a disconnector function or a current-carrying element with a disconnector function and at least one further function, i.e. a combined device, is formed.

A continuation of the concept according to the invention for the arc fault monitoring device can consist in that a current measurement is implemented via a Rogowski coil or another current measuring device or a device with a measuring function and with at least one further function.

It corresponds to a special embodiment of the concept according to the invention for the arc fault monitoring device that the current measurement is arranged between a main busbar and a field rail or in front of the protective device of a branch at the connection to the field rail in a switchgear.

An extension of a special embodiment of the concept according to the invention for the arc fault monitoring device can provide that the respective branches are designed in fixed and / or plug-in technology with the arc fault monitoring device, with the current measurement taking place directly after the connection to a field rail. For the exemplary embodiment of a feeder using withdrawable technology, this solution can also be used to protect the isolating contacts from overload when there is a permissible high current flow per time.

A continuation of the concept according to the invention for the arc fault monitoring device can consist in protecting the respective isolating contacts of the feeders in slide-in technology and contacting surfaces on the field rail from damage by excessively large currents per unit of time by means of the acquisition and calculation module.

Further embodiments and advantages of the invention are explained below using exemplary embodiments and using the drawing.

• Fig. 1 in einer schematischen Darstellung ein Abgangsfeld insbesondere einer Niederspannungsschaltanlage mit Abzweigen in Festeinbau- und Einschubtechnik;
• Fig. 2 in einer seitlichen Schnittdarstellung einen erfindungsgemäßen Schaltanlagenaufbau mit Abzweigen, vertikalen Feldverteil- bzw. Steckschienen, horizontalen Hauptsammelschienen, die Lage der Rogowskispulen auf einer Verbindung zwischen einer vertikalen Feldverteil- bzw. Steckschiene und einer horizontalen Hauptsammelschiene und das Erfassungs- und Berechnungsmodul für eine erfindungsgemäße Störlichtbogenüberwachungseinrichtung auf einer Feldschiene;
• Fig. 3 in einer perspektivischen Darstellung den Aufbau eines erfindungsgemäßen Abzweigmoduls in Einschubtechnik mit dem Erfassungs- und Berechnungsmodul für die kontinuierliche Ermittlung der I² x t- Werte und einem Hauptschalter mit seinen primärseitigen Anschlüssen;
• Fig. 4 in einer Draufsicht ein erfindungsgemäßes Abzweigmodul in Einschubtechnik;
• Fig. 5 in einer perspektivischen Darstellung einen vergrö-ßerten Ausschnitt aus Fig. 4 mit eingangsseitigen Trennkontakten und die gleich im Anschluss je Phase für die Stromerfassung angeordneten Rogowskispulen oder vergleichbaren Elemente zur Stromerfassung.

It shows:

• Fig. 1 a schematic representation of an outgoing panel, in particular a low-voltage switchgear with branches in fixed-installation and withdrawable technology;
• Fig. 2 In a sectional side view, a switchgear assembly according to the invention with branches, vertical field distribution or plug-in rails, horizontal main busbars, the position of the Rogowski coils on a connection between a vertical field distribution or plug-in rail and a horizontal main busbar and the detection and calculation module for an arc fault monitoring device according to the invention a field rail;
• Fig. 3 in a perspective view the structure of a branching module according to the invention using plug-in technology with the acquisition and calculation module for the continuous determination of the I ² x t values and a main switch with its primary-side connections;
• Fig. 4 in a plan view of a branching module according to the invention using slide-in technology;
• Fig. 5 an enlarged section in a perspective view Fig. 4 with isolating contacts on the input side and the Rogowski coils or comparable elements for current detection arranged immediately afterwards for each phase for current detection.

Fig. 1 shows an outgoing panel 1, in particular of a low-voltage switchgear with branches 2 in fixed-installation and withdrawable technology.

In Fig. 2 an inventive switchgear structure is shown with branches 2, vertical field distribution or plug-in bars 3, horizontal main busbars 4, the Rogowski coils 5 on a connection between a vertical field distribution or plug-in busbar 3 and a horizontal main busbar 4 and the acquisition and calculation module 6 for a Arc fault monitoring device according to the invention on a field rail.

Fig. 3 shows the structure of a branching module according to the invention using plug-in technology with acquisition and calculation module 6, for example for the continuous determination of the I ² x t values and a main switch 7 with its connections 8 on the primary side.

Fig. 4 in a plan view of a branching module according to the invention in slide-in technology with isolating contacts 9 and the Rogowski coils 5 for current measurement.

In Fig. 5 are in an enlarged section Fig. 4 input-side isolating contacts 9, the Rogowski coils 5 arranged behind them for each phase for the current detection and the detection and calculation module 6 shown in a branch module.

The arc fault monitoring device according to the invention is characterized in that arcing faults or faults in front of the branch protection device are detected by monitoring and evaluating the currents and I ² x t values in outgoing panels or branches of low-voltage switchgear. If significantly higher I ² x t values are recorded than the protective devices in the outgoing bays or branches allow, there must be a primary-side fault or a failure of the protective device. If such an error is detected, an AQD is activated and the infeed switch or a high-speed disconnector is triggered, whereby the error is switched off within a few milliseconds. The resulting damage is minimized through the rapid detection and deactivation of a primary fault. The field rail and the input-side isolating contacts of the withdrawable unit are thus protected from damage.

List of reference symbols

1

Departure field

2

Branch

3

vertical field distribution or plug-in rail

4th

horizontal main busbar

5

Rogowski coil or equivalent element for current measurement

6th

Acquisition and calculation module

7th

Main switch

8th

primary-side connection

9

Isolating contact

Claims (11)

Arc fault monitoring device, in particular for low-voltage switchgear with feeder panels and output panels (1), characterized in that a detection and calculation module (6) is arranged in the output panels (1) or in the respective branches (2) therein, which measures a current flow per unit of time evaluates and reliably differentiates an arc fault that has arisen in front of the respective protective device from a normal short circuit. Arc fault monitoring device according to Claim 1, characterized in that the acquisition and calculation module (6) determines and evaluates the I ² * t values in the microsecond range. Arc fault monitoring device according to claim 1 or 2, characterized in that fuses and / or MCCBs (Molded Case Circuit Breakers) and / or current-carrying elements with a protective function and / or current-carrying elements with a protective function and at least one other are used as protective elements in the branches (2) Function are arranged. Arc fault monitoring device according to one of Claims 1 to 3, characterized in that a current flow above a current limit specified by the protective devices for a regular current flow is stored as a faulty current flow in the acquisition and calculation module (6). Arc fault monitoring device according to one of Claims 1 to 4, characterized in that a short circuit is to be generated by means of an AQD device (Arc Quenching Device) in order to extinguish the arcing fault immediately in the event of a fault being detected. Arc fault monitoring device according to Claim 5, characterized in that the current flow is switched off downstream of the short circuit through the AQD via a feed switch. Arc fault monitoring device according to claim 5, characterized in that the current flow is switched off downstream of the short circuit via a disconnector or a disconnector or a current-carrying element with a disconnector function or a current-carrying element with a disconnector function and at least one further function. Arc fault monitoring device according to one of Claims 1 to 7, characterized in that a current measurement is implemented using a Rogowski coil (5) or another current measuring device or a device with a measuring function and at least one further function. Arc fault monitoring device according to claim 8, characterized in that the current measurement is arranged between a main busbar (4) and a field rail (3) or in front of the protective device of a branch at the connection to a field rail (3) in a switchgear. Arc fault monitoring device according to one of Claims 1 to 9, characterized in that the respective branches (2) are constructed using fixed-installation and / or slide-in technology. Arc fault monitoring device according to one of claims 1 to 10, characterized in that the respective isolating contacts (9) of the branches (2) in slide-in technology and contacting surfaces on the field rail (3) against damage by excessively high currents per time unit are to be protected by means of the acquisition and calculation module (6).

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